ena: Upgrade ena-com to freebsd v2.7.0

This commit introduces a number of infrastructures in ena-com, some of
which are being used as of ENA v2.7.0 while other certain infrastructure
assets have been made available for potential future application.

Upgrade ena-com to include the following changes:

• Introduce customer metrics infrastructures
• Introduce SRD metrics infrastructures
• Remove unused fields from ena_com_io_cq and ena_com_io_sq structs
• Minor rework of ena_com_fill_hash_function
• Introduce PHC infrastructures
• Update the licenses for ena-com files
• Delete duplicate *_defs.h found in ena-com and ena_defs directories
• Add validation for completion descriptors consistency
• Move ena_fbsd_log.h file to ena_plat.h

Approved by: cperciva (mentor)
Sponsored by: Amazon, Inc.